There is no detection. I've said this before and i'll say it again because skids like Alex here have no clue what they're talking about. GTA cannot detect memory editing as it stands. Their entire detection process is the oldest one in the books, common sense. If you're reported and R* notices that someone with 10 hours of gameplay has earned 5-10M in car sales and is level 100+... it's very clear foul play was at hand. Not only that but i'm sure they can go into the transaction and see what was sold for what.